Nian Qiong, Wang Yuefeng, Yang Yingling, Li Ji, Zhang Martin Y, Shao Jiayi, Tang Liang, Cheng Gary J
School of Industrial Engineering, Purdue University, West Lafayette, IN, USA.
School of Materials Engineering, Purdue University, West Lafayette, IN, USA.
Sci Rep. 2014 Oct 20;4:6612. doi: 10.1038/srep06612.
Synthesis of diamond, a multi-functional material, has been a challenge due to very high activation energy for transforming graphite to diamond, and therefore, has been hindering it from being potentially exploited for novel applications. In this study, we explore a new approach, namely confined pulse laser deposition (CPLD), in which nanosecond laser ablation of graphite within a confinement layer simultaneously activates plasma and effectively confine it to create a favorable condition for nanodiamond formation from graphite. It is noteworthy that due to the local high dense confined plasma created by transparent confinement layer, nanodiamond has been formed at laser intensity as low as 3.7 GW/cm(2), which corresponds to pressure of 4.4 GPa, much lower than the pressure needed to transform graphite to diamond traditionally. By manipulating the laser conditions, semi-transparent carbon films with good conductivity (several kΩ/Sq) were also obtained by this method. This technique provides a new channel, from confined plasma to solid, to deposit materials that normally need high temperature and high pressure. This technique has several important advantages to allow scalable processing, such as high speed, direct writing without catalyst, selective and flexible processing, low cost without expensive pico/femtosecond laser systems, high temperature/vacuum chambers.
合成多功能材料金刚石一直是一项挑战，因为将石墨转化为金刚石所需的活化能非常高，因此阻碍了其在新型应用中的潜在开发。在本研究中，我们探索了一种新方法，即受限脉冲激光沉积（CPLD），其中在限制层内对石墨进行纳秒激光烧蚀可同时激活等离子体并有效地对其进行限制，从而为从石墨形成纳米金刚石创造有利条件。值得注意的是，由于透明限制层产生的局部高密度受限等离子体，在低至3.7 GW/cm(2)的激光强度下（对应于4.4 GPa的压力）就已形成纳米金刚石，这远低于传统上将石墨转化为金刚石所需的压力。通过控制激光条件，用这种方法还获得了具有良好导电性（几kΩ/Sq）的半透明碳膜。该技术提供了一条从受限等离子体到固体的新途径，用于沉积通常需要高温高压的材料。该技术具有几个重要优势，可实现可扩展加工，如高速、无需催化剂的直接写入、选择性和灵活加工、无需昂贵的皮秒/飞秒激光系统、高温/真空腔室的低成本。
